Known machines for packaging rolls of paper, and of the type described, for example, in U.S. Pat. No. 5,433,063, normally comprise a wrapping unit for forming a tubular wrapping from a continuous web of heat-seal material; feeding groups of rolls of paper successively into the tubular wrapping, so that each group is located between two free tubular portions of the tubular wrapping; and transferring the tubular wrapping and the groups to a sealing station at a first constant travelling speed.
The sealing station comprises at least two sealing units, each of which comprises at least two sealing bars moving in time with each other along a substantially horizontal sealing path to feed a group of rolls of paper along the sealing path and seal a said free tubular portion.
The sealing bars of each sealing unit are mounted on two respective pairs of belt conveyors, which are located on opposite sides of the sealing path, in a substantially vertical direction crosswise to the sealing path, and which form part of a relative actuating device also comprising an electric motor common to all the belt conveyors of the actuating device.
Each electric motor is operated independently of the electric motors of the other sealing units to feed the relative sealing bars, and hence the relative groups of rolls of paper, along the sealing path at a second travelling speed, which is variable so that, by combining the first and second travelling speed, each free tubular portion is folded substantially onto the relative groups of rolls of paper.
Since the output rate is proportional to the number of sealing units employed, known packaging machines of the type described above are equipped with a relatively large number of sealing units, and consequently also with a relatively large number of belt conveyors, which make them relatively complex and expensive.